Properties of Cement Mortar Containing Recycled High-Density Polyethylene (HDPE)

Abstract

Millions of tons of plastic waste are generated globally, and only about 10 percent of it is recycled. It is crucial to segregate and circulate plastic waste and repurpose it for countless other uses. There are many ways to repurpose and reuse these discarded plastics. One use that can be examined is the use of plastic as a partial sand replacement in cement mortar. To contribute to this important and valid discourse, this research studies the mechanical and thermal properties of cement mortar that incorporates recycled high-density polyethylene (HDPE) particles. Different percentages (0%, 4%, 6%, and 10%) of sand replacement by volume with recycled HDPE particles are tested. Two different cement-sand ratios are investigated: 1:3 and 1:6. The experiments include compressive and indirect tensile strengths, unit weight, and thermal conductivity. Experimental results show that the increase in plastic content in mortar mixtures results in a decrease in the compressive and tensile strengths as found in the literature. On the other hand, a decrease in the thermal conductivity of the cement mortar that incorporates HDPE particles is also observed. For HDPE/sand replacement of 10% and cement to sand at a ratio of 1:3, the reduction in the thermal conductivity coefficient k is 50%. For HDPE/sand replacement of 10% and cement to sand at a ratio of 1:6, the reduction is 32%. This reduction is of significance as the cement mortar is usually used for stucco. When used for southern façades in arid climate countries like Egypt, producing stucco with such low thermal conductivity will result in a reduction in energy consumption for the AC. Moreover, the aesthetic value of the colored stucco may lead to the elimination of the painting process, not to mention the positive impact on the environment.